利用膜生物反应器处理农药废水的研究

采用一体式膜生物反应器工艺,以农药生产废水为处理对象,研究了pH值、营养和进水化学需氧量(CODCr)对膜生物反应器处理效果的影响。结果表明,膜生物反应器对农药废水中的CODCr、农药、浊度和臭等有很好的去除效果,其对污染物的去除率受pH及进水CODCr影响较大,最佳pH为8.0,最佳进水CODCr为1 500 mg/L。营养盐的添加对污染物去除率影响不大,在低浓度时有一定的促进作用。在最佳操作条件下,膜生物反应器对农药生产废水中的CODCr、农药总含量、乙草胺、异丙甲草胺、丁草胺、丙草胺和浊度的去除率分别为81.9%、94.9%、94.0%、88.6%、99.7%、97.5%和100%。     

Chloroacetanilide herbicide-induced rat enterochromaffin cell tumors: a case study within the context of the IPCS framework,for analyzing the relevance of a cancer mode of action for humans

The WHO International Programme on Chemical Safety (IPCS) framework for analyzing the relevance of a cancer mode of action (MoA) for humans (IPCS cancer-HRF) is an application to assess human relevance of tumorigenic hazards found through rodent bioassays. The chloroacetanilide herbicides, butachlor and alachlor, induced enterochromaffin-like (ECL) cell tumors in rat stomachs, at the highest doses. This study analyzed the human relevance of this tumor by applying the IPCS cancer-HRF using published data. In a postulated MoA, early key events (KEs) included decreased mucosal thickness in the fundic region, due to reduced parietal cells. The following KEs included increased pH of gastric acid and hypergastrinemia, leading to enhanced cell proliferation and hyperplasia, and resulting in the outcome of an ECL cell tumor. The data showed consistencies in dose-response and temporal concordance with the KEs and specificity in the tumor response, providing strengthened evidence of the KEs. While the early KE was not the same, similar MoAs have already been established for omeprazole and ciprofloxacin. The integrated data indicated that the postulated MoAs were biologically plausible. Alternative MoAs were excluded.. Based on sufficient evidence, an MoA was established in rats. When addressing chemically inducible MoAs of human relevance, KEs of hypergastrinemia and trophic ECL cell hyperplasia were judged to not be qualitatively and quantitatively plausible in humans. The MoA in rats is unlikely to be present in humans; however, the potential effects on parietal cells cannot be excluded. Thus, the IPCS cancer-HRF is very useful for assessing human relevance.     

Acetochlor sorption and degradation in limestone subsurface and aquifers

BACKGROUND: Acetochlor, introduced on the market in 1994, is used extensively worldwide, but sorption and degradation studies, including subsurface, are scarce, and there appear to be no such studies with aquifer sediment according to the present mini‐review. Sorption, degradation and mineralisation of acetochlor were investigated in heterogeneous limestone down to 43 m below surface (mbs) in four European aquifers (1.7–59 mbs), both aerobic and anaerobic. RESULTS: Sorption revealed K_d values of 3.39–4.96 L kg^?1 in topsoil, < 0.01–2.02 L kg^?1 in heterogeneous limestone, 0.06–0.72 L kg^?1 in aerobic aquifers and 1.03–4.60 L kg^?1 in microaerobic or anaerobic aquifers. The mineralisation half‐lives in the samples from 0.0–0.6 mbs were 0.8–2.1 years and 4.7–95 years in the unsaturated limestone samples from 1–43 mbs. Out of 22 samples from four different European aquifers, acetochlor was mineralised in five samples (half‐lives of 9–19 years), all from the same aquifer and core section (19.25–19.53 mbs). CONCLUSION: Sorption was weak in limestone and aerobic sandy aquifers, and strong in topsoils and in reduced sandy aquifers. Redox conditions controlled the extent of acetochlor sorption in aquifers, as reduced conditions induced increased sorption. Acetochlor was mineralised in deep subsurface, though slowly, and, as mineralisation is the only true removal mechanism in natural attenuation, even slow mineralisation in aquifers with long residence times can have a significant impact. Copyright © 2010 Society of Chemical Industry